100 LINKS WITH THE PAST [ch. 



evidence of more tlian superficial agreement with 

 those of tlic recent species. The task of deciphering 

 the past history of plants, particularly of the Conifers, 

 is accompanied by many difficulties and insidious 

 temptations. It is clear from a critical examination 

 of many of the recorded instances of fossil Sequoias 

 that the generic name has been frequently used by 

 writers without adequate grounds. The fragmentary 

 specimens available to the botanical historian cannot 

 as a rule be subjected to microscopical investigation, 

 and even a partial acquaintance with the similarity 

 of the foliage of different types of living Conifers is 

 sufficient to convince the student of the need of self- 

 control in the identification of the fossils. It is, 

 how^ever, easy to point out obvious pitfalls, though 

 difficult to maintain a judicial attitude in the 

 excitement of endeavouring to interpret documents 

 which are too inconq^lete to be identified with 

 certainty. If w^e put on one side all records of 

 supposed fossil Sequoias not based on satisfactory 

 data, there remains a wealth of material testifying to 

 the antiquity of the surviving species. 



It is by no means improbable that Conifers 

 closely allied to the RedAvoods and Mammoth trees 

 of California were represented in Jurassic floras ; 

 but hitherto no proof has been obtained of the 

 occurrence of a Sequoia among the rich material 

 aflbrded by the Jurassic plant-beds of Yorkshire 



