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relatively higher position in the plant-world than 

 that which is now held by their diminutive de- 

 scendants. It is, however, impossible to get away 

 from the conclusion that the oldest Palaeozoic floi'a 

 of which we have an intimate knowledge must be 

 the product of development of an age which is 

 represented by a chapter in the history of the plant 

 kingdom at least as far removed from the beginning 

 as it is separated from the chapter now being written. 

 Examples might be quoted in illustration of the risks 

 attending the determination of fossils by means of 

 external features alone, but it may suffice to mention 

 the case of a specimen originally described as a 

 fragment of a Cretaceous Dinosaur under the name 

 AacJienosmiriis multidens. By the examination of 

 thin sections this supposed bone was shown to be 

 a piece of Dicotyledonous wood (42). The methods of 

 preservation of plants as fossils are numerous and 

 varied and the few examples selected give but an 

 incomplete idea of the subject : for a fuller treatment 

 of fossilisation the reader is referred to more technical 

 treatises (48 vol. i.). 



The employment of fossil plants as ' Thermometers 

 of the ages ' is a branch of Palaeobotany to which a 

 passing allusion may be permitted though it is only 

 indirectly connected with the main question. As 

 one of the most interesting examples of changed 

 climatic conditions revealed by a study of fossil plants, 



